1. Field of the Invention
The present invention relates generally to the field of gear reducers and similar products for transmitting mechanical power from a prime mover to a driven load. More particularly, the invention relates to a sealing system for maintaining lubricant in a gear reducer, and for preventing or reducing the ingress of foreign contaminants, including solid and liquid contaminants into the machine from the environment.
2. Description of the Related Art
Gear reducers are employed in a wide variety of applications throughout all facets of industry. In general, gear reducers are employed where a desired speed at an application is reduced with respect to an output speed of a prime mover, such as an electric motor or internal combustion engine. Similarly, speed reducers are used to amplify torque provided by a prime mover. It should be noted, that as used herein, the term xe2x80x9cspeed reducerxe2x80x9d should be understood to include similar machines, whether employed to reduce speeds of a prime mover or, conversely, to increase speeds of a prime mover as may be the case in certain applications.
Gear reducers typically include one or more stages of reduction, depending upon the overall level of reduction desired. For a single reduction stage, the machines may include an input shaft or hub and an output shaft or hub, each carrying gearing which intermeshes to provide a reduction ratio as defined by the gearing configuration. Input shafts in such machines often include a small gear or pinion formed on or mounted to the shaft, while the output shaft or hub typically includes a larger gear wheel supported on the output member. In multi-stage gear reducers, similar intermeshing gear sets are provided for successive reduction in stages, with intermediate stages generally including jack shafts which may be fully enclosed within the gear reducer housing. In machines of this type, the overall gear reduction is a product of the reduction ratio of the successive stages.
Gear reducers have found a wide range of applications in industry. While certain applications are less demanding, many subject the gear reducer to extremely difficult environmental conditions. For example, in mining, material handling, and other applications, gear reducers may be employed to transport various solid and liquid materials, such as via belt conveyors, screw conveyors, augers, and so forth. In these applications, products from the environment, typically liquids, dust and debris can be transmitted to the rotating machinery and ingress into the interior of the gear reducer, or be lodged in the vicinity of the rotating shafts or hubs used to transmit power into and out of the machine. A challenge, then, in such applications continues to be preventing such ingress of foreign contaminant materials so as to protect the bearings and other internal components of the gear reducer.
Another difficulty in applications calling for gear reducers and similar rotating machinery involves the containment of lubricant within the gear reducer housing. To maintain smooth operation of the gear reducer, gear reducer housings are typically filled with a lubricating oil which coats intermeshing and rotating surfaces to maintain smooth operation. Such lubricant is often provided up to a desired level somewhat below the top of the gear reducer internal cavity, such as to a level of an uppermost rotating assembly. The lubricant also provides cooling for the internal components.
Attempts have been made to address the foregoing concerns through the use of various seal arrangements. For example, various types of seal assemblies have been provided at input and output shaft interfaces, both on the gear reducer housing itself, and on various brackets or adapters interfaced with the housing. In the case of shaft-mounted gear reducers, a particular difficulty arises in that the rotating shaft or hub may actually convey contaminants, particularly liquid or semi-liquid contaminants, directly to the seal assembly. Through continuous rotation of the input or output shaft or hub, these materials may progressively ingress into the gear reducer, ultimately resulting in degradation in performance and possible mechanical damage.
There is a need, therefore, for an improved technique for sealing gear reducers, particularly gear reducers designed for mounting to an input or output shaft. There is a particular need for an improved sealing approach which serves both to effectively preclude the ingress of solid and liquid contaminant products from the environment, while maintaining fluid lubricant within the gear reducer housing during operation.
The invention provides a technique for sealing a gear reducer designed to respond to these needs. The technique may be employed in newly designed products or, in appropriate situations, may be retrofitted into existing machines, replacing lower performance sealing assemblies at one or multiple locations where input or output shafts or hubs traverse housing barriers. The technique provides a multiple-level or compound sealing arrangement which includes a combination of mechanical shields or barriers, and soft seals which ride against a rotating component, typically the input or output shaft or hub. Sealing passages, including labyrinths, and cavities are defined between the sealing components to provide additional barriers to the ingress of foreign contaminants and to the flow of internal lubricants from the gear reducer housing. The entire sealing assembly may be designed to fit flush with an external surface of the housing, or may be recessed, providing a lip or pilot surface for interface adapters, and so forth. External sealing components, such as lip seals or V-seals may be provided to add an additional barrier outboard of the internal and recessed seal assemblies.
In the presently preferred configuration, a first seal assembly is positioned inboard of a second seal assembly. Both seal assemblies are recessed within an aperture to which a rotating component, such as a hub or shaft, extends. The first seal assembly includes a soft seal biased into contact with the rotating member. The second seal assembly includes a metal shield to which a soft seal is secured. Both soft seals ride against the rotating member during operation. Additional contact portions of the seals may be provided, particularly for the first seal assembly, so as to define a plurality of sealing cavities between the contact portions of the seal assemblies. The shield of the second seal assembly fits closely around the rotating member, but does not contact the rotating member. A labyrinth is defined between the shield and the rotating member, eliminating most solid contaminants or debris from contact with the soft seals. An additional face-riding seal may be provided external to the first and second seal assemblies, providing an external barrier to the contaminants.